Brain anatomy

This page is a dumping ground for anatomical terms that come up in conversation with neuroscientists, phrased (hopefully!) in a way that CS people can understand them and locate them in the brain. Click a tract name for more detailed information, including instructions for segmenting the tract out of a tractogram in Brainapp.

A sagittal section of a human brain. Click this image for a high-res version in which you can read the annotations.

Cingulum / cingulum bundle

White matter fibers located just superior to the corpus callosum, but running anterior-posterior. In a para-sagittal section, they look like a letter C turned on its side, with the tips pointing inferior, stacked right on top of the CC. In a coronal section, they look like two small circles just superior to the CC on either side of the interhemispheric fissure.

Corona radiata

A fan-shaped sheet of WM that radiates superior (upward) from the brain stem to the cortex in each hemisphere. The fibers of the corona radiata run superior-inferior, and the fanning is anterior-posterior. The sheet is flat and thin in the left-right dimension; its orientation is approximated by a sagittal cutting plane.

Corpus callosum (CC)

The large tract of left-right-running fibers connecting the hemispheres. In a mid-sagittal cutting plane, it looks like a letter C turned on its side, with the tips pointing inferior. See [1]. Moving around the CC from the back (posterior), it is subdivided into parts named:

Splenium

The posterior, slightly bulbous part of the CC.

Body

The more-or-less flat part of the CC between the splenium and the genu.

Genu

The anterior part of the CC, where it bends back on itself. "Genu" means "knee".

Rostrum

The part of the CC inferior and posterior to the genu.

Corticospinal tract (CST)

A major descending pathway that projects from the cerebral cortex to the spinal cord. It is the key pathway for voluntary movement (contrast it with the other major longitudinal but ascending pathway: the dorsal-column medial lemniscal system). Also, this is a good point to remember that tracts are generally named in source-to-target fashion. For example, corticospinal tract originates from the cortex and projects to the spinal cord, similarly corticobulbar tract goes from the cortex to the bulbar (well, brain stem), etc.

Forceps major / forceps posterior

The posterior projection of the CC (from the splenium) into the occipital lobe (the back of the brain). In a transverse section, it looks like a letter C at the posterior portion of the brain with the tips pointing posterior. See [2].

Forceps minor / forceps anterior

The anterior projection of the CC (from the genu) into the cerebrum (the front of the brain). In a transverse section, it looks like a letter C at the anterior portion of the brain with the tips pointing anterior. In other words, it looks sort of like a pair of mandibles over the eyes. See [3].

Fornix

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Inferior longitudinal fasciculus (ILF)

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Internal capsule

White matter structure that runs between the cortex and medulla, containing major longitudinal (both ascending and descending) pathway systems, including the corticospinal tract, dorsal column medial lemniscus (DCML) system (only medial lemniscus part), corticobulbar tract, etc.

Superior longitudinal fasciculus (SLF)

???

Thalamus

Major relay nuclei (a gray matter structure) in the diencephalon (division of the brain primarily containing thalamus and hypothalamus in mature brain). Most sensory information is carried to the thalamus first (i.e., via ascending tracts) and then relayed to the cerebral cortex. Similarly, neural signals controlling movements, learning, memory and emotions bound to sub-cortical structures are relayed by the thalamus to their final destinations.

Uncinate fasciculus

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External Links

• Biology-Online dictionary --- search for text descriptions of terms
• U. Arkansas neuroanatomy atlas images
• Radiopaedia --- a wiki encyclopedia for radiology; search for articles